1. Field of the Invention
The present invention relates generally to the field of encapsulated hardware which may be made resistant to caustic materials by using a chemically resistant encapsulation material around a nut or bolt or the like, such as for use in sealing tanks which hold such caustic materials, including by way of example, hydrogen-sulfide, brine, oil, wheat, grain and other materials. The present invention relates more specifically to a method and the resulting product thereof, constituting an encapsulated nut which has a stove pipe shape designed to surround all the exterior surfaces of a standard nut, while providing an elongated cylindrically shaped tube attached thereto for receiving a threaded bolt through the nut.
2. Prior Art
The concept of encapsulating a nut for use in a caustic environment, is an old one. Typically, such nuts are encapsulated with a material resistant to caustic environments. Such materials, by way of example, may include a resistant plastic such as Nylon, Delrin or Noryl. A search of the prior art relevant to the present invention has indicated the following patents as being pertinent:
______________________________________ 3,557,654 Weidner Jr. 3,618,444 Kay et al 3,693,495 Wagner 4,154,138 Melone 4,557,654 Masuda et al 4,582,462 Thiel 4,883,399 MacLean 4,887,950 Sakayori et al 4,907,929 Johnston Jr. 4,962,968 Caplin 4,993,902 Hellon ______________________________________
U.S. Pat. No. 4,887,950 to Sakayori et al is directed to a waterproof nut for use inside a water storage tank constituting a metallic nut body coated with a synthetic resin and including a cap portion for accommodating the free end of a bolt that projects from the rear surface of the nut. A nut body 1, with a hexagonal outer periphery and internal thread, is coated with a nylon resin layer 2. The resin layer forms a front surface with a lip 4 that covers the front of the nut and a cap-shaped portion 5 for accommodating the free end of the bolt B at the rear of the nut. The lip 4 has a step 7 or a tapered portion 8 to position a packing material. The cap portion may be formed with an internal thread and an external shape for a fastening tool.
U.S. Pat. No. 4,883,399 to MacLean is directed to a plastic encapsulated nut and washer assembly for sealing, providing a lock nut function, and protecting the projected threads of the threaded member and nut assembly. The assembly 10 includes a common hex nut 12 with threaded bore 14 and faces 16, 18 and includes an ordinary washer 20. A cap screw 42 with hex head 44 and threaded shank 40, extends through the bores 34 and 36 of the external parts being fastened, through bore 22 of washer 20 and is screwed into the threaded bore 14 of the encapsulated hex nut 12. The body 50 formed of molded reasonably rigid plastic material, is molded in place around hex nut 12 with a lip 56 to loosely retain the washer 20. The intermediate body portion 60 has a cup-shaped portion 70 with a cap 68 that has a bore sized to be an interference fit on the cap screw, thus providing a lock nut function.
U.S. Pat. No. 4,557,654 to Masuda et al is directed to a resilient nut cover of plastic or rubber for seating and protecting a nut and the projecting screw thread of a bolt. The cover 1 for nut 11 has, in the basal portion 2a, a protruding portion 5 that engages groove 13 on the nut. The cover also has a screw thread 10 in the end portion 2b for providing a disengagement proof means to engage the threaded end of the bolt 15. If the dimension of the base is determined so that the cover is pressed onto the face of the fastened piece 16, then rain and corrosive gas will be prevented not only from the connection between the nut and the bolt, but also between the nut and the fastening piece 16.
U.S. Pat. No. 4,993,902 to Hellon is directed to a plastic capped lock nut assembly that provides protection for exposed threads of a threaded rod or other element extending outwardly of the bore of the lock nut body and ring. The lock nut includes a metal body 32 and a plastic cap 70, secured together by a lock ring 50. The lock ring 50 is secured to the metal body by turning in the flange 44 on the body to engage the shoulder 64 of the lock ring. The assembly is completed by sonic welding the cap 70 to the lock ring.
U.S. Pat. No. 4,907,929 to Johnston Jr. is directed to a cover for the end of a bolt to which a nut is attached. The cover is installed by means of an interference fit. The cover 20 has a body 24 of any suitable outer shape, and has an internal cavity 32 with a first section 34 and a second section 36. The first section 34 is configured to be the shape of the nut 18 to be covered. The second section is cylindrical and has a height greater than the height of the threaded bolt to be covered. The diameter of this cylindrical second section is less than the outer diameter of the threaded bolt 19, but greater than the inner diameter of the threads on bolt 19. This diameter provides an interference fit for the cover over the threaded bolt portion and since the material for the cover is polyurethane, hard rubber or plastic, the material will yield to allow installation.
The difficulty with the aforementioned prior art that is most relevant to the present invention is that it comprises an encapsulated nut having an extended bore, wherein the bore is either threaded or becomes threaded when the bolt thread extends beyond the nut and bites into the wall of a plastic or other material, thereby creating a thread therein. Unfortunately, such an internal thread adds to the resistance to the bolt as it is threaded through the nut and thus reduces the accuracy of torque readings between the bolt and nut. Furthermore, such close interface between the bore and the bolt prevents sealant flowthrough between the extended portion of the bolt and the bore, which could otherwise improve the seating when using a sealant which can otherwise flow through the gap between a non-threaded or smooth bore and a bolt thread. Thus, it would be advantageous if it were possible to provide an encapsulated nut having an extended bore which has a smooth surface that is larger in diameter than the threads of the bolt that is mated with the encapsulated nut.